The present invention relates to vehicles.
In particular, the present invention relates to off-the-road vehicles of the type which are adapted to travel on rough terrain such as, for example, a forest tractor.
The invention relates especially to elastically yieldable structures to be associated with frames of vehicles of the above type, these frames forming, for example, a cap of the vehicle as well as a load-carrying part thereof.
In known vehicles of the above type, such as forest tractors, the axle units usually are completely unsprung. The sole components which have any significant elasticity with such vehicles are the tires thereof. As a result, the dynamic behavior of such vehicles is unsatisfactory. This latter factor necessitates extremely slow speeds of travel for such vehicles since even at relatively low speeds the frames of such vehicles are subjected to powerful impact stresses and the forces of acceleration to which the operator of the vehicle is subjected are known to be dangerous to his health. While attempts have been made to correct these latter drawbacks, as by providing special seat designs for the vehicle operator, these latter attempts have proved to be of only minor beneficial significance. Experience has shown that it is particularly difficult to damp the lateral oscillations or accelerations of the vehicle by way of the construction of the seat thereof.
Various spring arrangements have been suggested for off-the-road vehicles of the above general type, and in this connection reference may be made to Swedish publication print No. 370,911 as well as to Finnish Pat. applications Nos. 3294/73 and 3518/74 both of which are publicly available. However, systems as shown in the latter publications have not proved to be fully satisfactory and have not gained any extensive use. The prior art constructions have not successfully isolated the driver of the vehicle from the frame oscillations, even through attempts have already been made to reduce the oscillation of the entire vehicle.